This invention relates in general to construction of rollers and in particular to a friction-driven roll having a supporting tube which is made up of a plurality of link sleeve members which is supported on a stationary core by means of a plurality of distension bodies.
Within the context of the present application, it is understood that a friction-driven roll is a roll which is not rotated by a drive of its own and is associated with a counter-roll or both. Such rolls are employed as gap pressure producing rolls, belt controlling rolls, curved spreader rolls, etc., for example in mangles, squeezers, calenders, printing machines, or paper making machines.
Known is a friction-driven roll in which only one distension body is provided between the stationary roll core and the supporting tube, at the side close to and remote from the counter-roll, respectively. Both these distension bodies embrace the roll core only in the respective diametrically opposite regions, and exend over the entire length of the core, without any subdivision. The distension bodies can be pressurized or depressurized by means of a fluid, to either press the jacket tube against the counter-roll, or lift it therefrom. The jacket tube forming the circumference of the roll is mounted on a supporting tube by means of circular bearings provided at spaced-apart locations.
Preferably, the jacket tube is supported at two locations only. In consequence, there is a risk of flection if a weblike sheet or strip is passed through the roll gap under pressure. The pressure is then distributed non-uniformly. In general, a uniform pressure distribution in the roll gap is required while treating such webs in manufacture. A flection of such prior art friction-driven roll cannot be corrected.
Further known is a friction-driven roll comprising a stationary roll core, in which the supporting tube is mounted for rotation on the core with the interposition of both anti-friction bearing and distension bodies, and has an elasticity bending jacket. In this prior art design, the supporting tube is sub-divided into drums, with the length of each drum corresponding to the spacing of the antifriction bearings or distension bodies. Already for this reason, only a relative coarse correction of the flexure can be obtained. Further, the supporting tube at the same time performs the function of the jacket tube and must therefore be relatively thick-walled, alrady for stability reasons. Such a supporting or jacket roll is little elastic and requires a counter-roll of a relatively large outer diameter, so that it is difficult to obtain a high specific gap pressure such as required for improving the squeezing effect (see British Pat. No. 1135901).